The ash, which has remained airborne over the rest of Europe, has fallen over parts of Iceland, covering some areas in ash up to four inches thick. It has fallen into lakes, creating a cement-like mud, and weighed down the wings of geese, preventing them from flying to safety.

But the real danger comes from inhaling or ingesting the fluoride-laden ash. Fluoride is, in small doses, an essential mineral. In high concentrations, however, it becomes toxic—a serious threat to unwitting livestock left outdoors and exposed.

Too much fluoride turns to acid in the animals' stomachs, which leads to hemorrhaging in the intestines. It also binds with calcium, making bones frail and brittle—even causing teeth to crumble.

The best we can do is put them in the barn, block all the windows, and bring them clean food and water as long as the earth is contaminated.

A group of farmers have banded together to help each other do just that. Pooling vehicles and barn space, the farmers drove around the island looking for horses that had panicked and fled during the ash fall.

In areas where there's ash fall and horses are outside, the conditions are terrible...they can't survive in this if it carries on too long. The horses have to be fed with hay and have access to running water to avoid them consuming a lot of ash.

Meanwhile, farmers wearing masks will be left to work through low visibility and toxic ash to protect their animals until conditions begin to improve.